This invention relates to decontamination techniques and, more particularly, to a method and apparatus for evacuating water from within nuclear reactor fuel rods and the like.
In order to function, nuclear reactors for power, research, or for any other purpose must have a sufficient concentration of fissionable material to sustain an essentially continuous sequence of fission reactions. This fissionable material, of which uranium dioxide (UO.sub.2) is typical, frequently is compacted into small pellets which are loaded into slender metal fuel rods. Other rods within the reactor core may contain non-fissile materials which are known as poisons. Such rods may often be more than six feet in length. After the pellets are loaded, the fuel rods are each capped and welded closed thus encapsulating the "fuel" material.
Removal of contaminants from the fuel rods has been accomplished by drilling a small hole in the fuel rod surface and applying a vacuum to the hole to purge the contaminants e.g. moisture and gases, from within the rod. It also might be necessary to pressurize the fuel rod by introducing an inert gas into the rod interior through the small hole after the contaminants are evacuated. The small hole may be sealed before the rod is removed from the controlled environment.
It has been found in some instances that the application of a vacuum to the small hole in the fuel rod is not adequate to evacuate all of the contaminants from within the rod. The remaining contaminants can lead to inefficient nuclear fuel consumption as well as swollen, burst or collapsed fuel rods.